Observation of the decay $ {B}_s^0\to {K}^0p\overline{p} $ and measurement of the $ {B}_{(s)}^0\to {K}^0p\overline{p} $ branching fractions

A study of the charmless baryonic decays ${B}_{(s)}^0\to {K}^0p\overline{p}$ is presented, where ${B}_{(s)}^0$ denotes either a B 0 or a ${B}_s^0$ meson. The analysis is based on proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb −1. The decay ${B}_s^0\to {K}^0p\overline{p}$ is observed for the first time, with a measured branching fraction of (9.14 ± 1.69 ± 0.90 ± 0.33 ± 0.20) × 10 −7 and a significance of 5.6σ. The uncertainties respectively account for statistical and systematic contributions, the precision of the branching fraction of the normalisation channel B 0 → K 0 π + π − and the fragmentation fraction ratio f s /f d . The branching fraction determined for ${B}^0\to {K}^0p\overline{p}$ is (2.82 ± 0.08 ± 0.12 ± 0.10) × 10 −6, which is the most precise measurement to date.